This invention relates to an improved animal feed supplement having reduced metal corrosion characteristics comprising an aqueous solution containing from 87-90 percent by weight 2-hydroxy-4-(methylthio)-butanoic acid, i.e. MHA.RTM. acid, and to the method for preparing same. FNT MHA is a registered trademark of Monsanto Company for 2-hydroxy-4-(methylthio)-butanoic acid.
The method for preparing MHA acid and its utility as an animal feed supplement are well known and set forth in commonly assigned U.S. Pat. No. 2,745,745 which is incorporated herein by reference. Such patent describes the preparation of MHA acid by hydrolysis of the corresponding cyanohydrin. Thus, the MHA-nitrile is hydrolyzed in excess aqueous mineral acid, such as hydrochloric acid or sulfuric acid, to afford the MHA acid and, e.g., ammonium chloride in a dilute aqueous hydrochloric acid slurry. The slurry is then dehydrated to remove water and aid in the precipitation of most of the ammonium chloride. During this process, most of the hydrochloric acid is also removed. The resulting thick slurry is then filtered and centrifuged to separate a further amount of ammonium chloride and then water is added back to dilute the mixture to a concentration of 87-90 percent by weight of MHA acid.
The acid solution thus prepared is suitable as an animal feed supplement but has presented problems in storage, transportation and handling in metal equipment because of its corrosion characteristics. Accordingly, the object of the present invention is to provide an aqueous MHA acid solution containing from 87 to 90 percent by weight MHA acid which shows reduced corrosion characteristics in contact with metal surfaces such as carbon steel, stainless steel and aluminum, such metals being used as materials of construction in storage, transportation and handling facilities.